A drive axle of a heavy vehicle generally includes a pair of axle shafts housed within a live or rigid axle housing for driving wheels secured to wheel hubs. When a vehicle is driven along a straight path, the wheel hubs will be turning at approximately the same speed, and the drive torque will be equally split between both wheels. When the vehicle negotiates a turn, the outer wheel has to travel over a greater distance than the inner wheel. A differential assembly allows the inner wheel to turn more slowly than the outer wheel as the vehicle negotiates a turn.
Many different kinds of differential gear have been proposed, but the most common consist of a casing in which two or four freely rotatable planetary gears are arranged in mesh with pinion gears of the vehicle drive shafts. The casing carries an annular crown wheel which is driven by a pinion of an input shaft which is itself driven from the vehicle engine.
An example differential assembly is described in EP 1591694.
Two main types of braking systems are used on heavy vehicles; drum brakes and disc brakes.
A drum brake generally has a pair of brake shoes pivotably mounted within the drum and moveable between an applied position and a released position. The applied position causing a wheel connected to the drum brake to brake, and the released position permitting free rotation of a wheel connected to the drum brake. The brake is actuated via an actuation shaft and an actuation device, to cause the brake shoes to move to the applied position. As the brake shoes wear, a slack adjuster adjusts the actuation device to account for the wear of the brake shoes. The slack adjusters typically need maintenance through the life of a brake. Current axle assemblies require removal of multiple components of the drum brake and movement of the actuation shaft, to remove the slack adjuster for maintenance. This is an inconvenient and time consuming process.
A disc brake generally has a brake disc located between two opposed friction elements. To brake a connected wheel, the friction elements are moveable to an applied position, i.e. into contact with the brake disc. On heavy vehicles, the brake disc is generally actuated to an applied position using a pneumatic system. Due to the number of components, including for example vehicle suspension, that need to be assembled to the chassis of a heavy vehicle, it is preferable to arrange components of an axle assembly in a compact manner.
There is therefore a need for an axle assembly that permits easy assembly/disassembly of the slack adjusters of a drum brake and/or has a compact arrangement.